title: Voltage-gating of Escherichia coli porin: a cystine-scanning mutagenesis study of loop 3.
abstract: Porins, such as Escherichia coli OmpF, provide the only reported example of a voltage-gated channel where the three-dimensional structure is known to high resolution. Mutations that affect voltage-gating are clustered around the eyelet region, which is a mid-channel constriction caused by a polypeptide loop (L3) folding inside the lumen of this beta-barrel pore. These data, combined with molecular dynamics simulations, indicate that voltage-gating may involve L3 displacement. We have constructed six double cysteine OmpF mutants, five of which form disulphide bonds fixing L3 in the conformation determined by X-ray crystallography. These channels have altered single-channel conductances but unimpaired voltage-gating. The data show that L3 movement is not required for voltage-gating.
authors.affiliation: Department of Biochemistry and Genetics, Medical School, University of Newcastle Upon Tyne, UK.
authors.forename: G
authors.initials: G
authors.lastname: Bainbridge
authors.forename: H
authors.initials: H
authors.lastname: Mobasheri
authors.forename: G A
authors.initials: GA
authors.lastname: Armstrong
authors.forename: E J
authors.initials: EJ
authors.lastname: Lea
authors.forename: J H
authors.initials: JH
authors.lastname: Lakey
mesh_terms: D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D003553:Cystine; D004220:Disulfides; D004926:Escherichia coli / Q000502:physiology*; D015640:Ion Channel Gating; D008051:Lipid Bilayers; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D018272:Porins / Q000737:chemistry* / Q000378:metabolism; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: D004220:Disulfides; D008051:Lipid Bilayers; C109237:OmpF protein; D018272:Porins; D011994:Recombinant Proteins; D003553:Cystine